/**
 * Copyright (C) 2002-2015   The FreeCol Team
 * <p>
 * This file is part of FreeCol.
 * <p>
 * FreeCol is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 * <p>
 * FreeCol is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * <p>
 * You should have received a copy of the GNU General Public License
 * along with FreeCol.  If not, see <http://www.gnu.org/licenses/>.
 */

package net.sf.freecol.common.networking;

import net.sf.freecol.common.model.Game;
import net.sf.freecol.common.model.TradeRoute;
import net.sf.freecol.common.model.Unit;
import net.sf.freecol.server.FreeColServer;
import net.sf.freecol.server.model.ServerPlayer;

import org.w3c.dom.Element;


/**
 * The message sent when assigning a trade route to a unit.
 */
public class AssignTradeRouteMessage extends DOMMessage
{

    /** The identifier of the unit. */
    private final String unitId;

    /** The identifier of the trade route. */
    private final String tradeRouteId;


    /**
     * Create a new <code>AssignTradeRouteMessage</code> with the
     * supplied unit and route.
     *
     * @param unit The <code>Unit</code> to assign a trade route to.
     * @param tradeRoute The <code>TradeRoute</code> to assign.
     */
    public AssignTradeRouteMessage( Unit unit, TradeRoute tradeRoute )
    {
        super( getXMLElementTagName( ) );

        this.unitId = unit.getId( );
        this.tradeRouteId = ( tradeRoute == null ) ? null : tradeRoute.getId( );
    }

    /**
     * Create a new <code>AssignTradeRouteMessage</code> from a
     * supplied element.
     *
     * @param game The <code>Game</code> this message belongs to.
     * @param element The <code>Element</code> to use to create the message.
     */
    public AssignTradeRouteMessage( Game game, Element element )
    {
        super( getXMLElementTagName( ) );

        this.unitId = element.getAttribute( "unit" );
        this.tradeRouteId = ( element.hasAttribute( "tradeRoute" ) )
                ? element.getAttribute( "tradeRoute" )
                : null;
    }


    /**
     * Handle a "assignTradeRoute"-message.
     *
     * @param server The <code>FreeColServer</code> handling the message.
     * @param connection The <code>Connection</code> message was received on.
     * @return An update containing the assignTradeRouted unit, or an
     *     error <code>Element</code> on failure.
     */
    public Element handle( FreeColServer server, Connection connection )
    {
        final ServerPlayer serverPlayer = server.getPlayer( connection );

        Unit unit;
        try
        {
            unit = serverPlayer.getOurFreeColGameObject( unitId, Unit.class );
        }
        catch ( Exception e )
        {
            return DOMMessage.clientError( e.getMessage( ) );
        }

        TradeRoute tradeRoute;
        if ( tradeRouteId == null )
        {
            tradeRoute = null;
        }
        else
        {
            try
            {
                tradeRoute = serverPlayer.getOurFreeColGameObject( tradeRouteId,
                                                                   TradeRoute.class );
            }
            catch ( Exception e )
            {
                return DOMMessage.clientError( e.getMessage( ) );
            }
        }

        // Proceed to assign.
        return server.getInGameController( )
                .assignTradeRoute( serverPlayer, unit, tradeRoute );
    }

    /**
     * Convert this AssignTradeRouteMessage to XML.
     *
     * @return The XML representation of this message.
     */
    @Override
    public Element toXMLElement( )
    {
        Element result = createMessage( getXMLElementTagName( ),
                                        "unit", unitId );
        if ( tradeRouteId != null )
        {
            result.setAttribute( "tradeRoute", tradeRouteId );
        }
        return result;
    }

    /**
     * The tag name of the root element representing this object.
     *
     * @return "assignTradeRoute".
     */
    public static String getXMLElementTagName( )
    {
        return "assignTradeRoute";
    }
}
